The subject invention relates generally to thermal ink jet printers, and is directed more particularly to a technique for reducing drive energy in thermal ink jet printheads while maintaining consistently high print quality.
Thermal ink jet printers utilize thermal ink jet printheads that comprise an array of precision formed nozzles, each of which is in communication with an associated ink containing chamber that receives ink from a reservoir. Each chamber includes an ink drop firing resistor which is located opposite the nozzle so that ink can collect between the ink drop firing resistor and the nozzle. The ink drop firing resistor is selectively heated by voltage pulses to drive ink drops through the associated nozzle opening in the orifice plate. Pursuant to each pulse, the ink drop firing resistor is rapidly heated, which causes the ink directly adjacent the thermal resistor to vaporize and form a bubble. As the vapor bubble grows, momentum is transferred to the ink between the bubble and the nozzle, which causes such ink to be propelled through the nozzle and onto the print media.
For ease of replacement of thermal printheads which eventually wear out, thermal printheads are often implemented as printhead cartridges comprising a thermal printhead and an ink reservoir. With such implementation, printhead driver circuitry is connected to the printhead cartridge by appropriate contacting components. An example of a thermal ink jet printhead cartridge is disclosed in "The second-Generation Thermal InkJet Structure," Askeland et al, HEWLETT-PACKARD JOURNAL, August 1988, pages 28-31.
Further background information on thermal inkjet printheads and/or the manufacture thereof can be found in commonly U.S. Pat. Nos. 4,746,935 and 4,809,428, and in the following publications: "Development of the Thin-Film Structure for the ThinkJet Printhead," Eldurkar V. Bhasker and J. Stephen Aden, HEWLETT-PACKARD JOURNAL, May 1985, pages 27-33; "Integrating the Printhead into the HP DeskJet Printer," J. Paul Harmon and John A. Widder, HEWLETT-PACKARD JOURNAL, October 1988, pages 62-66; and "The Think Jet Orifice Plate: A Part with Many Functions," Siewell et al., Hewlett-Packard Journal, May 1985, pages 33-37.
A consideration with thermal ink jet printers that utilize modular printhead cartridges is that the printhead driver circuitry commonly provides ink drop firing signals having generally constant energy to the ink drop generators of the printhead. However, different ink drop generator configurations and different inks may have different ink drop firing energy requirements. For example, an ink drop generator configured to produce smaller ink drops requires less energy for firing, and too much energy can cause improper operation. Also, a given printhead can have ink drop generators that are configured to provide respectively different ink drop volumes, for example, as disclosed in the above-referenced U.S. Pat. No. 4,746,935. Further, newly developed or revised printheads could have ink drop firing energy requirements that are different from those for which existing thermal ink jet printers have been configured.